In an optical recording device of the prior art, a socalled three-beam method is adopted in which laser beams are made into three diffraction beams by a diffraction grating as shown in FIG. 15. The diffracted beams are converged by a convergent lens whereby the diffracted beams are made main beams used for writing and reading the zero-order diffraction beams and the first-order diffraction beams are made tracking beams.
Tracking is performed in such a way that these two tracking beams are radiated on lines, several microns in width, which are positioned on both sides of an information unit row called a track guide 51 on an optical recording medium and a servo, which makes the amount of reflected light of both tracking beams equal, is then applied, as shown in FIG. 16.
As described above, the above-mentioned optical recording device of the prior art performs tracking by detecting light reflected from the optical recording medium for two tracking beams by using a photo detector. However, it has a drawback that in such a case where there are defects in the track guide 51 of an optical recording medium, tracking cannot be performed on those portions.